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OCR for page 219
5
Answers to the Military's Questions
This chapter summarizes answers to the specific questions that were posed
to the committee. In an attempt to summarize the answers, descriptions of criti-
cal issues are merely reviewed. For more details and in-depth discussions of the
critical issues the reader is referred to Chapters 2, 3, and 4 where full discus-
sions, including explanations of inconsistent results or needs for further research
for promising areas are included. Therefore, for each question and to avoid re-
dundancy, only a summary of the issues already addressed in other chapters are
presented here; the specific recommendations for each question are also included.
QUESTIONS 1 AND 2
1. Which dietary minerals are likely to have an impact on human per-
formance? Are these minerals provided in adequate amounts in the meals,
ready to eat (MREs) and the current first strike rations (FSRs)?
2. Is there a potential for any significant deficiency in essential miner-
als when soldiers subsist on (a) MREs during garrison training (i.e., intense
training and one-day missions) or (b) FSRs during combat missions (i.e.,
repeated cycles of three- to seven-day combat missions, with two- to three-
day recovery periods that include garrison dining)?
Questions 1 and 2 are closely related and will be addressed together. Based
on the military's information on mineral status and performance levels (Friedl,
2005; see Friedl in Appendix B) and the commmittee's experience with the
functions, metabolism, and nutrient intake requirements, six minerals--calcium,
copper, iron, magnesium, selenium, and zinc--were deemed important for mili-
tary performance.
219
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220 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
The committee used information (the mineral composition for 3 different
MREs containing 24 menus each and 3 different FSRs menus) provided by the
U.S. Army Research Institute of Environmental Medicine to evaluate the se-
lected minerals' content adequacy in the operational rations (see Appendix C).
Content adequacy can be evaluated considering groups (i.e., is the mineral con-
tent adequate for the population?) or individuals (i.e., is the mineral content
adequate for each individual?). Because the committee had no data on the distri-
bution of mineral intakes for military garrison training, the mineral content of
menus for the population could not be evaluated. Instead, the recommended
RDAMGT and AIMGT (Recommended Dietary Allowance and Adequate Intake
for military garrison training, respectively) were used as benchmarks to evaluate
mineral content adequacy of the various rations for individuals. (see Question 4
for the process on arriving at the new RDAMGT and AIMGT).
For this exercise, the committee assumed that women will consume two
MREs and men will consume three MREs. The average mineral content levels
for each MRE or FSR were used to assess adequacy; in other words, three MREs
or two MREs need to meet (without exceeding the Tolerable Upper Intake Lev-
els [ULs]), at the minimum, the specific RDAMGT and AIMGT recommended by
this committee for men and women, respectively. The content of one FSR needs
to be within the recommended range for assault rations (IOM, 2006). However,
consideration should be given to the fact that, although the average content might
be adequate, some menus within each ration seem to be low in specific minerals
(e.g., calcium). It was assumed for this study that the mix of menu choices eaten
daily are sufficient to meet the average level of the minerals of interest. How-
ever, individuals' repeated selection of MREs that have low levels of particular
minerals presents a risk of developing mineral deficiencies. The committee rec-
ommends, therefore, that menus on the low end of the mineral content range be
revised to meet the recommended intake levels for both men and women.
On average most mineral content in rations will meet the committee's rec-
ommendations (see Table 5-1, Chapter 3 for details). The exceptions are the iron
content for women (RDAMGT = 24 mg/day versus an average of 18 mg in two
MREs) and the zinc content for men (RDAMGT = 15 mg/day versus an average of
about 14 mg in three MREs) and women (RDAMGT = 11 mg/day versus an
average of about 9 mg in two MREs). The mineral content of the FSRs appears
to meet the recommendations of the current committee, except for calcium,
whose average content in the FSRs (673 mg) is slightly lower than recommended
in the Institute of Medicine (IOM) report, Nutrient Composition of Rations for
Short-Term, High-Intensity Combat Operations (750 mg, see Table 5-1) (2006).
The committee concluded that more research is needed on calcium intake
and any associated risk of kidney-stone formation before lowering the range of
calcium in assault rations below the AI of 1,000 mg/day.
The level of specific mineral intakes depends not only on the mineral con-
tent of the rations but also on the rations' composition (i.e., interaction with
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ANSWERS TO THE MILITARY'S QUESTIONS 221
TABLE 5-1 Mineral Intakes: Institute of Medicine Dietary Reference
Intakes, Current Military Dietary Reference Intakes, Recommended
Intakes for Garrison Training (EARMGT, RDAMGT, or AIMGT), and
Recommended Levels for Assault Rations
IOM RDA Levels For
Nutrient or AI MDRI RDAMGT or AIMGT Assault Rations*
Calcium (mg)
Male 1,000 1,000 1,000 750850
Female 1,000 1,000 1,000
Copper (µg)
Male 900 ND 1,800 9001,600
Female 900 ND 1,500
Iron (mg)
Male 8 10 14 818
Female 18 15 24
Magnesium (mg)
Male 420 420 420 400550
Female 320 320 320
Selenium (µg)
Male 55 55 55 55230
Female 55 55 55
Zinc (mg)
Male 11 15 15 1125
Female 8 12 11
NOTE: AI = Adequate Intake; EAR = Estimated Average Requirement; MDRI = Military Dietary
Reference Intake; MGT = military garrison training; ND = not determined; RDA = Recommended
Dietary Allowance.
*IOM (2006).
other components), food consumption behavior (e.g., do soldiers eat 100 percent
of the rations?), and ration selection. Therefore, the committee concluded that
surveys on actual mineral intake or status--especially for calcium and iron--
need to be conducted for the adequacy of the rations' mineral content to
be evaluated and that for food composition analysis should continue to be
performed.
QUESTION 3
3. During garrison training, do weight loss diets (energy or macronutri-
ent restricted) have the potential to lead to deficiencies of specific essential
minerals?
The principal determinant of mineral balance in healthy individuals who are
physically active is that there be an adequate intake of all essential nutrients.
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222 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
This situation would be the usual condition for soldiers in garrison training who
eat prepared foods or rations that have intakes meeting the military's dietary
reference intake (MDRI) requirements (U.S. Departments of the Army, Navy,
and Air Force, 2001). Under some field conditions, particularly during opera-
tions in training or active combat, weight loss primarily caused by inadequate
intakes in relation to increases in energy expenditure is common. However, un-
der other conditions weight constancy or even weight gain is common (as is
reported to be characteristic of the current operations in Iraq).
Mineral status during weight loss depends significantly on the severity of
caloric deprivation, macronutrient composition of the diet, and mineral intake.
The most severe caloric deficiency is due to total fasting, which would never be
intended during military operations. Without energy or mineral intake but with
adequate fluid intake, mineral balances would be negative for all of the minerals
under consideration, including calcium, magnesium, phosphorus, sodium, potas-
sium, zinc, selenium, copper, and iron. Such a regimen can be tolerated in obese
individuals for many months so long as there is sufficient fat and water, and very
obese individuals have tolerated fasting (receiving only noncaloric liquids) for
up to 249 days (Bloom, 1959; Runcie and Thomson, 1970; Thomson et al.,
1966). Even though there would be substantial lean-tissue loss (approximately
one-quarter to one-third of the weight loss) as well as bone loss and reduced
exercise capacity, death from protein-calorie malnutrition likely would occur
only when there was lean-tissue loss representing about one-half of the lean
tissue or about 40 percent of the initial body weight (Henry, 1990). Dysphoria,
postural hypotension, and changes in mood are frequent in the early stages of
starvation, but after initial adaptation to a fasting state (which occurs over the
first week or so), substantial deficits in physical performance are not found until
approximately a 10-percent weight loss is reached. For normal-weight individu-
als (the expectation is that most individuals found in military settings would be
of normal weight), total fasting is much less well tolerated, even initially. Mor-
tality would happen probably within 611 weeks, and physical performance
would be very poor in the later weeks. Death would take place due to an absence
of stored fat sufficient to meet the energy deficit; this claim is based on the
experience of the Irish Republican Army hunger strikers in Northern Ireland
(Leiter and Marliss, 1982). Thus, death usually would occur because of an acute
lack of energy caused by depleted body energy stores.
A less severe, but still hypocaloric, diet would be described as one that
provides some intake but less, often far less, than about 50 percent of caloric
needs. A substantial experience with such diets occurred in the 1970s when
liquid protein diets based on collagen were used as the principal source of pro-
tein and calories, leading to multiple mineral deficiencies. A number of deaths
occurred in obese individuals consuming such regimens for periods of at least
several months; the deaths were thought to be due to a combination of lean tissue
loss and mineral deficiencies, particularly of potassium, copper, and phosphorus
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ANSWERS TO THE MILITARY'S QUESTIONS 223
(Amatruda et al., 1983; Isner et al., 1979; Klevay, 1979). Subsequently, similar
degrees of caloric deprivation--but with adequate mineral and high biologic
value protein intake, as found in semistarvation ketogenic diets--were effective
for short-term weight loss of considerable degree without causing undue safety
concerns in obese individuals (Palgi et al., 1985). These cases of caloric depriva-
tion emphasize the importance of protein composition and mineral intake under
the related conditions. However, the use of this type of regimen for military
purposes was discontinued--except for unanticipated combat situations--after
experience with a severely hypocaloric diet, which met less than 50 percent of
the energy needs during Ranger training, led to substantial and unacceptable
clinical deficits associated with greater than 10-percent weight loss (Moore et
al., 1992).
Caloric deficits of about 1,0001,500 kilocalories that still provide greater
than 50 percent of caloric needs are well tolerated clinically for weight loss in
the overweight and obese as well as during short-term military operations (IOM,
2006). Similar diets used for intentional weight loss on an outpatient basis rarely
lead to a 10-percent weight loss, frequently because of a lack of compliance, and
thus, lead to unchanged or even improved physical performance. In military
combat settings, where other food sources are unavailable, it would be good
clinical policy to avoid prolonged periods of hypocaloric feeding, which could
lead to weight losses greater than 10 percent.
The principal variables, in terms of mineral balance, of these mildly hypo-
caloric diets are the macronutrient content (particularly if high or low in protein)
and the mineral content. The minerals of greatest interest are calcium, magne-
sium, and zinc, since the likely duration of use intended in a military context
makes substantial imbalances for iron, copper, and selenium of little clinical
relevance, particularly when these minerals are provided daily in MDRI quanti-
ties. Of the three minerals of greatest interest, magnesium is the least likely to
present a clinical problem, because the body can reduce urinary magnesium
losses to minute levels, even without limiting magnesium intake. Zinc is of
greater concern because of its importance in immune function and the potential
for occurrence of diarrheal illness in military operations [as mentioned in Hamer
(2005) and in Hamer in Appendix B, diarrhea is a risk factor for zinc losses]. If
however there is an absence of diarrhea and if zinc is consumed at MDRI quan-
tities, then the net zinc lost due to weight loss on a hypocaloric diet reflects net
nitrogen loss. Thus, minimization of net nitrogen loss would be the greater con-
cern when compared with zinc loss.
Studies of elemental balance in underweight subjects have demonstrated
that lean tissue has a fixed ratio of nitrogen to potassium, phosphorus, and so-
dium, and the three latter must all be provided in minimal amounts for lean
tissue to be maintained (Rudman et al., 1975). However, these amounts are met
easily by each of the minerals' RDA. Calcium balance under these conditions is
dependent on phosphorus and sodium, since bone-mineral repletion can not oc-
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224 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
cur in the absence of these elements (Rudman et al., 1975). Thus, the most
important variable is a relatively high protein intake of 1.21.5 g/kg (IOM, 2006);
benefits of a high-protein diet include a reduction in hunger (when compared
with an isocaloric diet high in carbohydrates) as well as a number of metabolic
benefits related to insulin action (Noakes et al., 2005). Bone turnover was in-
creased with both the high-protein and high-carbohydrate diets and included an
increase in both serum osteocalcin and urinary collagen cross-link excretion,
markers of bone resorption (Noakes et al., 2005).
The iron status (also of both diets) was well maintained and indicated no
changes in hemoglobin, even though dietary iron reached RDA levels only in the
high-protein diet (Noakes et al., 2005). This finding is in contrast to that of
Kretsch et al. (1998) where research indicated that obese women consuming a
diet providing approximately 50 percent of estimated calories led to a significant
reduction in hemoglobin and hematocrit and a reduction in cognitive ability
related to sustained attention. The difference in findings may be linked to the
iron status at the beginning of the diet period, which appeared to be better in the
former study, and perhaps as well to the higher protein intake particularly in the
high-protein group (Kretsch et al., 1998; Noakes et al., 2005). The protein intake
in the Kretsch et al. (1998) study was not regulated and, thus, was likely to be
less than 1 g/kg.
A number of studies have demonstrated the importance of higher protein in-
takes to improve preservation of lean tissue during weight loss when the protein is
substituted with isocaloric amounts of carbohydrate (Baba et al., 1999; Farnsworth
et al., 2003; Piatti et al., 1994). However, similar benefits in terms of hunger
reduction and improvement in lipid metabolism can be achieved if the carbohy-
drates are provided in larger quantities as long as those used have a low glycemic
index (Pereira et al., 2004). Nonetheless, for the maximal preservation of body
protein with weight loss, protein intakes of 1.21.5 g/kg would need to be present.
When the dietary protein is in this range, whether the protein is mostly from high-
calcium dairy products (2,400 mg/day) or from mixed-protein and moderate cal-
cium products (500 mg/day of calcium), the effects on fasting insulin, lipids, blood
pressure, and fibrinolysis and endothelial function (i.e., metabolic parameters) are
independent of diet (Bowen et al., 2005). A study from the same group did show,
however, that the lower calcium intake caused a larger increase in urinary
deoxypyridinoline as a marker of bone breakdown and an increase in osteocalcin
in the mixed-protein diet, only suggesting a benefit for the high-dairy protein with
its higher calcium in reducing bone turnover (Bowen et al., 2004).
Calcium is the principal mineral of concern regarding weight loss diets,
because its metabolism may be altered by dietary composition. Evidence shows
that weight loss--in overweight and obese subjects as well as in postmenopausal
women consuming their usual calcium intake--is associated with a loss in bone
mass (Hannan et al., 2000; Ricci et al., 2001) and an increase in fracture risk
(Langlois et al., 1996). Although many minerals are essential for bone health and
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ANSWERS TO THE MILITARY'S QUESTIONS 225
function, the risk of calcium inadequacy in the diet is higher than risks of other
deficiencies. Because of its role in bone health and potential alterations in me-
tabolism if intake is inadequate, calcium is the principal mineral of concern
regarding weight loss diets. In overweight postmenopausal women, weight loss
resulting from moderately hypocaloric intakes leads to reduced calcium absorp-
tion, but net positive calcium balance can be achieved with 1.8 g/day of calcium
as compared to 1.0 g/day (Cifuentes et al., 2004). A follow-up study demon-
strated that calcium supplementation at 1.7 g/day minimizes bone loss during
weight loss in overweight postmenopausal women (Riedt et al., 2005). An ear-
lier study on obese postmenopausal women also showed that calcium supple-
mentation of 1 g/day reduced urinary collagen pyridinium crosslinks, osteocalcin,
and parathormone during weight loss (Ricci et al., 1998). The effect was not
observed in obese premenopausal women (Shapses et al., 2001).
The relationships between weight loss, level of protein intake, calcium in-
take, and bone health have not been studied in physically active premenopausal
women, a population that would be relevant to the military. However, to safe-
guard against potential bone deficiency during weight loss higher protein intakes
and calcium intakes of at least 1 g/day--with, perhaps, even greater benefit if
intakes are in the 1,5001,700 mg/day range--are recommended. These recom-
mended intake levels should be tested on young adults who are intentionally
dieting for weight loss; if weight loss is a consequence of the training itself and
the reduced energy intakes found in military scenarios, then, the high protein/
high calcium intake should be tested in not obese, or even overweight soldiers.
With regard to weight loss and its impact on the other essential minerals--
including magnesium, zinc, selenium, copper, and iron--there is little evidence
to show that there is either (1) a reduced efficiency of use, and thus a need for
increased mineral intakes, or (2) a reduced need for mineral intakes during peri-
ods of modest hypocaloric intakes (1,0001,500 kcal/day) that provide at least
50 percent of daily caloric needs. Hence, providing the essential minerals in the
amounts proposed in this report should be sufficient to maintain optimal function
during weight loss.
QUESTION 4
4. Do the high-performance activities of soldiers cause excessive min-
eral loss, thereby raising the mineral dietary requirements?
There is evidence to believe that exercise-related mineral loss, occurring
mainly through the sweat but also through feces and urine, might be significant.
However, many of the studies addressing mineral secretion and exercise cannot
be applied to the military environment, or have design flaws, or both. Nonethe-
less, because of the number of studies suggesting that the losses are real, the
committee has increased the requirements for iron, copper, and zinc, based on
the best available data and on their expertise and reasonable judgements (see
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226 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
Table 5-1). Chapter 3 details the recommendations. These values should be con-
sidered provisional and should be reconsidered after new studies (following the
design recommendations in Chapter 4) become available.
The data for copper are variable partially due to differences in sweat collec-
tion and copper quantification methods. Based on the best data available, the
committee concluded that male soldiers in garrison training will lose at least 500
µg/day of copper (female soldiers will lose at least 350 µg/day) through sweat.
The data on iron, with regard to sweat losses, come from civilian studies and
vary considerably. However, the committee concluded that sweat losses might
be significant during exercise and need to be considered when establishing iron
requirements. The committee believes soldiers could lose as much as 1 mg/day
of iron (0.6 mg/day for women) through sweat.
Likewise, studies on zinc increases in the sweat generated by exercise reveal
that as much as 2.0 mg/day and 1.3 mg/day, for men and women, respectively,
could be lost because of garrison training conditions.
Calcium requirements may also be higher under the stress of physical activity
and environmental conditions normally experienced by military personnel in garri-
son training. There is evidence indicating that factors like increased sweat losses,
loss of bone mass with oral contraceptives, or increased losses with weight loss
could raise the requirements. Other factors encountered during training, however,
such as the beneficial effects of exercise on bone metabolism, may compensate for
those losses. All these various factors that affect calcium and bone metabolism act
concomitantly and the overall impact of garrison training on requirements is still
uncertain. The committee concluded that there is not enough evidence to change
the calcium dietary requirements for soldiers in garrison training but urged re-
searchers to conduct appropriate studies that could address this issue.
In all cases, acclimatization to heat and exercise is likely to occur, but ques-
tions regarding the extent of acclimatization remain unanswered. In addition,
new models (designed according to Chapter 4's recommendations) that better
simulate military garrison training conditions need to be developed, and the
resulting data on mineral losses must be collected. There was not enough data to
assess whether or not physical activity would increase urinary or fecal mineral
losses. However, there are suggestions to this effect (i.e., substantial fecal iron
losses could occur with extreme exercise); research in this area also is warranted
(see Chapter 4).
Nutrient standards for military personnel in garrison training or in opera-
tions should be derived as indicated in Box 5-1. Based on the sweat loss find-
ings, the committee adjusted the IOM Estimated Average Requirements (EARs)
and calculated new EARs and RDAs (EARsMGT and RDAsMGT) for copper, iron,
and zinc (see Table 5-1). The committee recommends using the current IOM AI
level of calcium for the general population as the AIMGT until more research
becomes available (see Table 5-1).
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ANSWERS TO THE MILITARY'S QUESTIONS 227
BOX 5-1
Establishing Nutrient Standards for Military Personnel
Recommendation: Nutrient standards for military personnel in garrison training
should be derived as follows:
1. EARMGT : Modify the current IOM EAR by adjusting for the variable of interest
(e.g., level of sweat losses).
2. RDAMGT : Add 2 × SD (standard deviation) of the EARMGT, to ensure that 97
98 percent of soldiers will have adequate intake.
There were not enough data addressing the impact of sweat losses on mag-
nesium and selenium levels to recommend an increase in dietary intake (see
Chapter 3 for details). Research on sweat, urinary, and fecal losses under mili-
tary garrison training conditions also is warranted (see Chapter 4). The commit-
tee recommends using the current IOM RDAs for magnesium and selenium for
the general population as the RDAMGT until more research becomes available
(see Table 5-1).
QUESTION 5
5. Is there any scientific evidence that mineral supplements (individu-
ally or in combination) improve soldiers' performance?
There is no definitive evidence that specific mineral supplementation in
amounts greater than those recommended as dietary requirements will improve
soldiers' physical or cognitive performance. Therefore, the committee has not
recommended the intake of supplements to this effect. There are, however, sci-
entific studies that strongly suggest the potential for improved performance and
are summarized below (see Chapter 3 for details).
A positive relationship between physical activity and calcium intake on bone
density has been demonstrated in postmenopausal women and children, although
not in age groups or lifestyles relevant to the military (Lau et al., 1992; Prince et
al., 1991; Specker, 1996; Specker and Binkley, 2003). However, related research
with premenopausal women has shown mixed results (Recker et al., 1992;
Valimaki et al., 1994). The type of exercise may influence bone turnover as well
as dietary intake. In research conducted on cadets, only males showed that milk
consumption positively influences bone health; there was also a significant im-
pact on cortical thickness related to milk consumption and exercise (Nieves,
2005; see Nieves in Appendix B). Calcium also appears to improve mood states,
especially premenstrual distress syndrome (PMS) and depression (Penland and
Johnson, 1993; Thys-Jacobs et al., 1989). Although results are encouraging for
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228 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
calcium to relieve negative mood states, this has been done only with civilians
and nonstressful situations; this suggestion needs to be demonstrated under the
environmental and stressful conditions of garrison training. The reader is re-
ferred to Chapter 3 for more details.
Although the few studies performed in the military population do not sug-
gest a relationship between iron status and cognition and mood states, there is
sufficient evidence from studies in the civilian population that supports an asso-
ciation between iron status and improved cognitive functions and behavior (e.g.,
Bruner et al., 1996; Groner et al., 1986, see Chapter 3). Some of these conclu-
sions come from studies on iron deficiency. One of the pieces of evidence comes
from a 16-week intervention study using women who, as part of the study, were
provided with iron supplements (see Beard and Murray Kolb in Appendix B).
After 16 weeks, some women had improved their iron status independently of
the iron supplementation. There was a strong association between the women
who reached the highest iron status (due to iron supplementation or other rea-
sons) and improved measurements of attention, learning skills, and memory func-
tions. Although one cannot ensure that iron supplementation will have a benefi-
cial effect in all cases, it appears that improved iron status, possibly beyond the
current recommended 15 µg/L of ferritin (level at which iron stores are present),
may have beneficial effects in cognitive functions relevant for the military.
Studies conducted to determine the effects of iron supplementation on mood
states also indicate that depression can be alleviated by treating iron deficiency
(Beard et al., 2005; Corwin et al., 2003). Although there is no doubt that the data
are promising, all of the studies linking cognition and behavior with iron status
have been done with civilians. Therefore, the committee concluded that before
requirements for iron are increased with the objective of improving cognitive
performance or mood states, more research is needed focusing on the subjects
and environment of interest to the military.
A few studies also have been performed on the potential relationship be-
tween magnesium nutrition and improved effects of sleep deprivation that might
affect future recommendations for military personnel. The association between
selenium and zinc and mood states also has garnered interest. The data for these
relationships, though, are still preliminary and, thus, merely suggestive.
Taken all the research together, the committee concluded there is no scien-
tific evidence to raise the recommendations for minerals with the objective of
improving physical or cognitive performance or behavior. The committee also
determined that it would be worthwhile to allocate enough resources for answer-
ing questions on the potential effects of supplemental calcium on physical per-
formance and mood states, supplemental iron on cognitive functions, and supple-
mental magnesium on sleep deprivation effects and mood states. In addition, the
relationship between supplemental zinc and cognition and mood states, as well
as supplemental selenium and improvement of mood states, also could be con-
sidered (see Chapter 4).
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ANSWERS TO THE MILITARY'S QUESTIONS 229
QUESTION 6
6. Are the Military Dietary Reference Intakes (MDRIs) for dietary min-
erals reflective of the Institute of Medicine (IOM) Dietary Reference In-
takes (Recommended Dietary Allowances [RDAs] or Adequate Intakes
[AIs])? Should the MDRIs follow the IOM RDA or AIs or should differ-
ences persist because of the specific needs of soldiers?
The MDRIs have been developed as a variant of the IOM Dietary Reference
Intakes (DRIs) to account for the different environments and physical activity
encountered by soldiers and to plan appropriate nutrient intakes and rations for
them. The MDRIs and the nutritional standards for operational rations (NSORs)
were established most recently in 2001 and were based on the IOM DRIs that were
current at that time (U.S. Departments of the Army, Navy, and Air Force, 2001).
Many of the MDRI values are similar to the DRIs, with the notable exception of
sodium. The current MDRIs for minerals are the same as the IOM RDAs or AIs.
There are reasons, however, to establish reference nutrient intakes that would
apply specifically to the military population and help them to maintain a nutrient
balance. First, the military population is different from civilians in terms of
anthropometric criteria--that is, military personnel are slightly different in
height, weight, and body fat and are generally more physically fit--and perfor-
mance activity levels (typically higher in soldiers). Mineral values in the MDRIs
should reflect the differences in anthropometry and in the mineral losses caused
by high-performance activity.
Second, the military lifestyle includes unique circumstances that are rarely
encountered by civilians. These circumstances include multiple physical and
psychological stressors (e.g., intense and continuous exercise while carrying
heavy weight, sleep deprivation, stressful combat situations, extreme weather
conditions) that can alter a soldier's physiology.
The third reason for establishing military-specific nutrient requirements is to
optimize the health and performance of enlisted men and women. The criteria
for establishing requirements for the general population by the IOM has been to
maintain health, so most of the data would ideally come from balance studies.
However, one of the military's main objectives is to suceed in operations that
demand ultimate physical and cognitive performance--consequently, if perfor-
mance benefits are demonstrated, then the military would recommend higher
nutrient levels. As science emerges regarding the unique nutrient needs of mili-
tary personnel, additional adjustments will be necessary to meet those needs.
The MDRIs should continue to reflect the IOM DRIs, with modifications
made to specific nutrient requirements if sufficient scientific evidence demon-
strates related needs and benefits. Also, the MDRIs can be used as guidelines for
rations development for the individual soldier.
The IOM DRIs can be used for dietary assessment and planning to guaran-
tee a low prevalence of inadequate nutrient intakes (IOM, 2000, 2003). To plan
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230 MINERAL REQUIREMENTS FOR MILITARY PERSONNEL
menus or rations for a large group, planners should know the EAR (and its
distribution) of the target population, not only the mean and standard deviation,
but also the percentile intake levels. However, when planning diets for individu-
als, using only the RDAs or AIs is appropriate and sufficient (IOM, 2003). The
MDRIs could be used to plan and assess menus for military personnel in the
same way that the IOM DRIs are used for civilians.
The difficulty in assessing the nutritional adequacy of menus for soldiers in
garrison training is, as mentioned previously, that determinations will depend
not only on the mean or median intakes but also on the range of the intake
distribution, which is unknown for the military population. Instead, MDRIs could
be used by cafeteria menu planners as a useful benchmark for what levels of
nutrients are needed in foods on the menus. The IOM report Applications in
Dietary Planning (IOM, 2003) should serve as a guide for using the MDRIs to
plan the diets of military personnel. For the present, food-service managers
should guarantee that cafeteria food is nutritionally diverse (contains selections
from all food groups) and adequate, so that the options offered are likely to meet
an individual's MDRI. To assist in the design of cafeteria food choices, food-
service managers should include dietitians and nutritionists who are capable
of applying nutrition guides, such as the Dietary Guidelines for Americans
(http://www.healthierus.gov/dietaryguidelines/) and MyPyramid (http://www.my
pyramid.gov/), that will meet the military's needs.
Although the nutrient intake levels for soldiers who eat rations are unknown,
it can be assumed safely that they will not vary too much if all of the rations
issued are consumed. When planning, rations should meet the new military
MDRIs (RDAMGT or AIMGT) for minerals. In situations where gender differences
exist, rations should contain the highest recommended amounts, but those
amounts should remain lower than the UL for the age range. Hence, the current
NSORs based on MDRIs are established to represent the minimal levels of nutri-
ents in operational rations. When adjusted as described, RDAMGT (and AIMGT)
would be the basis of NSORs and would provide adequate levels for military
personnel in garrison training.
The committee supports the use of NSORs--modified accordingly as new sci-
entific data become available--as minimum levels of nutrients in operational rations.
The NSORs might vary depending on specific military situations; for instance,
NSORs for military garrison training and for sustained operations may differ.
QUESTION 7
7. How do changes in drinking water sources during military deploy-
ment affect the balance of essential dietary minerals (e.g., U.S. public water
supply versus bottled water versus field purification water)?
The military's great efforts to educate soldiers on the need for water con-
sumption have resulted in an improved conciousness regarding water intake.
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ANSWERS TO THE MILITARY'S QUESTIONS 231
Consequently, water could become a method to deliver minerals. By virtue of
the diverse water sources processed for the military, water could be a source of
mineral intake variation with potential consequences on military performance.
However, due to purification processes, it appears that the mineral content of the
water for consumption is fairly low and would not contribute significantly to
dietary intakes of minerals.
The military provides soldiers with water from sources that meet the stan-
dards for chemical and microbiological levels. During foreign deployments,
drinking water may come from local water supplies and undergo additional treat-
ments such as filtration and chlorination for bacterial control and removal of
dissolved solids. For example, currently deployed soldiers consume mineral wa-
ter that is produced at eight different sites and inspected by the military for
bacteria, contaminants, and mineral content. In order for the water to be shipped
to the soldiers, the mineral content has to be as low as what is found in U.S.
commercially available mineral water; minerals are added in some cases (e.g.,
calcium is added to improve the taste). Soldiers also have access to nonbottled
water that is essentially mineral free because it has been filtered through reverse
osmosis purification units. The bioavailability of each mineral from water would
depend on the salt form in the water. However, scant research exists to suggest
that water can be a source of essential minerals.
Considering the typical water consumption volumes of approximately 3 L/
day, the committee concluded that due to processes applied to fresh water for
human consumption, differences in mineral content of water are not such that
will affect the total intake levels of minerals by military personnel and do not
contribute to the balance of essential dietary minerals. The committee concluded
that the addition of calcium and magnesium to water consumed by military per-
sonnel is warranted only when improving the taste is the desirable outcome.
There is no evidence to suggest that the addition of substantial levels of calcium
and magnesium would be an efficient strategy to meet nutritional standards; in
addition, there is little research on bioavailability of minerals from water. Addi-
tional cost evaluation of using water as a vehicle for minerals should be con-
ducted if it is to be considered for implementation.
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Representative terms from entire chapter:
calculated values
